If they're reference quality in ears then you will still gain improved sound through a proper headphone amp as channel separation, soundstage and how each instrucment and vocals are presented all boil down to the quality of the DAC/amp being used. Its worth noting that some mobos have high quality DACs and headphone amps built in and give you the option to swap out the OpAmps as you see fit. My mobo is an ancient Gigabyte Z170X Gaming 5 and has exactly that. This could be a cheap option to explore as OpAmps will change how the sound is presented and something like a Burr Brown OpAmp swapped in mght be a cost effective way to get some good quality heapdhone output if you so wished.
Otherwise external DAC with quality components and completely disable onboard sound is the ideal way to go and you don't need to worry when you upgrade your PC etc.
On the topic of sound, the 3045 arrived today...
A few annoyances like NAD still using the plastic side panels but this time round it's not the rubbery horrible material they used in the 7050. The updated remote is also a world ahead of the old one. No more sticky rubbery finish. Sound is where it counts and this is louder than my old one at half the cost. Happy!
Typically yeah, but I like minimalism and having another box using up a power socket and more cables cluttering up the workspace isn't my bag! Thankfully the NAD has a constant 60wpc in 4 and 8 ohms, with up to 200w available dynamically. 600ohm headphones supported too so hopefully assuming NAD fixed the longevity issues of the 7050, this should last me a very long time. Need to go touch some wood now.
skirting was just resting against the wall at that point. 
